Coupling to the lower-hybrid resonance

The transmission coefficient of a plane electromagnetic wave into a cold, inhomogeneous, mag­netized, deuterium plasma half-space and its eventual absorption at the lower-hybrid layer is com­puted numerically for a wide range of parameters. It is found that TM (transverse magnetic) waves incident at small angles with the vacuum-plasma interface couple into the plasma provided that ω/ω ci ≲ 20. Assuming that coupling to the lower-hybrid resonance in the cold-plasma approxima­tion is an indication of accessibility to the ion-cyclotron-harmonic waves in the hotplasma case, an alternative statement of the results obtained is that efficient coupling is possible from the second till the twentieth harmonic of the ion gyrofrequency using an antenna that launches TM waves at an approximately grazing incidence on the plasma surface. Simple configurations for coupling rf energy into thermonuclear plasma are suggested.